Question 1133045: Radium 221 has a half life of 30s. If a sample contains 96 units of radium 221, how much would remain after each time has elapsed?
a) 30 seconds
b) 2 mins.
c) 5mins
Answer by ankor@dixie-net.com(22740)   (Show Source):
You can put this solution on YOUR website! Radium 221 has a half life of 30s.
If a sample contains 96 units of radium 221, how much would remain after each time has elapsed?
:
The radioactive decay formula: A = Ao*2^(-t/h), where
A = amt remaining after t time
Ao = initial amt (96 units)
t = time is seconds
h = half-life of substance (30s)
:
a) 30 seconds
A = 96*2^(-30/30)
A = 96*2^-1
A = 96(1/2)
A = 48 units
:
b) 2 mins. that's 120 sec
A = 96*2^(-120/30)
A = 96*2^(-4), use your calc
A = 96*.0625
A = 6 units after 2 min
:
c) 5mins, that's 300 sec
A = 96*2^(-300/30)
A = 96*2^(-10)
A = 96*.00975625
A = .09375 units after 5 min
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